Take a mild soap, even like body wash is OK, squirt a small amount (like what you'd put in a sponge or slightly less) and put in a little cup. Fill the cup with tepid water (cold if you have stains) and swish the soap around. Dip a toothbrush in there and then firmly (but not roughly) brush the uppers. Dry with a very soft towel or a fresh flannel. I have those white/silver ultraboosts and they get dirty AF every other wear, my girlfriend also trashes her pink uncaged ones running. I clean them both and they look great. The bigger issue is snags, I snagged a pair of AceControl Boosts on my hi-hat stand and it was very delicate to repair.

I like those Lillards, Bounce cushioning is nice when done right. The next Lillards will have it also. Just one sort of side release of his with Boost. I am not obsessed with Boost for basketball, in fact more times than not it has come out kinda poorly.